\documentclass{article} 
\usepackage{tikz} 

\begin{document} 

\begin{tikzpicture}[>=latex,scale=2]
  \foreach \x in {-1, 0, 1} {
    \foreach \y in {0, 1, 2} {
      \path node (\x-\y) at (\x+\y-1, \y-\x) {};
    }
  }
  % \path[->] (0-0) edge [bend right = 30] (0-1);

  \node (a) at (0,0) {a};
  \node (b) at (10em,10em) {b};
  \path[->] (a) edge node (c) [above] {lianweidong} (b);
  \node [above] at (c.north) {haha};

\end{tikzpicture}

\end{document}
